/*
 * Copyright 2002-2021 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.method;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.MessageSource;
import org.springframework.context.i18n.LocaleContextHolder;
import org.springframework.core.BridgeMethodResolver;
import org.springframework.core.MethodParameter;
import org.springframework.core.ResolvableType;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.core.annotation.SynthesizingMethodParameter;
import org.springframework.http.HttpStatus;
import org.springframework.lang.NonNull;
import org.springframework.lang.Nullable;
import org.springframework.util.*;
import org.springframework.web.bind.annotation.ResponseStatus;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.StringJoiner;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

/**
 * Encapsulates information about a handler method consisting of a
 * {@linkplain #getMethod() method} and a {@linkplain #getBean() bean}.
 * Provides convenient access to method parameters, the method return value,
 * method annotations, etc.
 *
 * <p>The class may be created with a bean instance or with a bean name
 * (e.g. lazy-init bean, prototype bean). Use {@link #createWithResolvedBean()}
 * to obtain a {@code HandlerMethod} instance with a bean instance resolved
 * through the associated {@link BeanFactory}.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @author Sam Brannen
 * @since 3.1
 */
public class HandlerMethod {

    /**
     * Logger that is available to subclasses.
     */
    protected static final Log logger = LogFactory.getLog(HandlerMethod.class);

    private final Object bean;

    @Nullable
    private final BeanFactory beanFactory;

    @Nullable
    private final MessageSource messageSource;

    private final Class<?> beanType;

    private final Method method;

    private final Method bridgedMethod;

    private final MethodParameter[] parameters;

    @Nullable
    private HttpStatus responseStatus;

    @Nullable
    private String responseStatusReason;

    @Nullable
    private HandlerMethod resolvedFromHandlerMethod;

    @Nullable
    private volatile List<Annotation[][]> interfaceParameterAnnotations;

    private final String description;


    /**
     * Create an instance from a bean instance and a method.
     */
    public HandlerMethod(Object bean, Method method) {
        this(bean, method, null);
    }

    /**
     * Variant of {@link #HandlerMethod(Object, Method)} that
     * also accepts a {@link MessageSource} for use from sub-classes.
     *
     * @since 5.3.10
     */
    protected HandlerMethod(Object bean, Method method, @Nullable MessageSource messageSource) {
        Assert.notNull(bean, "Bean is required");
        Assert.notNull(method, "Method is required");
        this.bean = bean;
        this.beanFactory = null;
        this.messageSource = messageSource;
        this.beanType = ClassUtils.getUserClass(bean);
        this.method = method;
        this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
        ReflectionUtils.makeAccessible(this.bridgedMethod);
        this.parameters = initMethodParameters();
        evaluateResponseStatus();
        this.description = initDescription(this.beanType, this.method);
    }

    /**
     * Create an instance from a bean instance, method name, and parameter types.
     *
     * @throws NoSuchMethodException when the method cannot be found
     */
    public HandlerMethod(Object bean, String methodName, Class<?>... parameterTypes) throws NoSuchMethodException {
        Assert.notNull(bean, "Bean is required");
        Assert.notNull(methodName, "Method name is required");
        this.bean = bean;
        this.beanFactory = null;
        this.messageSource = null;
        this.beanType = ClassUtils.getUserClass(bean);
        this.method = bean.getClass()
                .getMethod(methodName, parameterTypes);
        this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(this.method);
        ReflectionUtils.makeAccessible(this.bridgedMethod);
        this.parameters = initMethodParameters();
        evaluateResponseStatus();
        this.description = initDescription(this.beanType, this.method);
    }

    /**
     * Create an instance from a bean name, a method, and a {@code BeanFactory}.
     * The method {@link #createWithResolvedBean()} may be used later to
     * re-create the {@code HandlerMethod} with an initialized bean.
     */
    public HandlerMethod(String beanName, BeanFactory beanFactory, Method method) {
        this(beanName, beanFactory, null, method);
    }

    /**
     * Variant of {@link #HandlerMethod(String, BeanFactory, Method)} that
     * also accepts a {@link MessageSource}.
     */
    public HandlerMethod(String beanName, BeanFactory beanFactory, @Nullable MessageSource messageSource,
                         Method method) {

        Assert.hasText(beanName, "Bean name is required");
        Assert.notNull(beanFactory, "BeanFactory is required");
        Assert.notNull(method, "Method is required");
        this.bean = beanName;
        this.beanFactory = beanFactory;
        this.messageSource = messageSource;
        Class<?> beanType = beanFactory.getType(beanName);
        if (beanType == null) {
            throw new IllegalStateException("Cannot resolve bean type for bean with name '" + beanName + "'");
        }
        this.beanType = ClassUtils.getUserClass(beanType);
        this.method = method;
        this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
        ReflectionUtils.makeAccessible(this.bridgedMethod);
        this.parameters = initMethodParameters();
        evaluateResponseStatus();
        this.description = initDescription(this.beanType, this.method);
    }

    /**
     * Copy constructor for use in subclasses.
     */
    protected HandlerMethod(HandlerMethod handlerMethod) {
        Assert.notNull(handlerMethod, "HandlerMethod is required");
        this.bean = handlerMethod.bean;
        this.beanFactory = handlerMethod.beanFactory;
        this.messageSource = handlerMethod.messageSource;
        this.beanType = handlerMethod.beanType;
        this.method = handlerMethod.method;
        this.bridgedMethod = handlerMethod.bridgedMethod;
        this.parameters = handlerMethod.parameters;
        this.responseStatus = handlerMethod.responseStatus;
        this.responseStatusReason = handlerMethod.responseStatusReason;
        this.description = handlerMethod.description;
        this.resolvedFromHandlerMethod = handlerMethod.resolvedFromHandlerMethod;
    }

    /**
     * Re-create HandlerMethod with the resolved handler.
     */
    private HandlerMethod(HandlerMethod handlerMethod, Object handler) {
        Assert.notNull(handlerMethod, "HandlerMethod is required");
        Assert.notNull(handler, "Handler object is required");
        this.bean = handler;
        this.beanFactory = handlerMethod.beanFactory;
        this.messageSource = handlerMethod.messageSource;
        this.beanType = handlerMethod.beanType;
        this.method = handlerMethod.method;
        this.bridgedMethod = handlerMethod.bridgedMethod;
        this.parameters = handlerMethod.parameters;
        this.responseStatus = handlerMethod.responseStatus;
        this.responseStatusReason = handlerMethod.responseStatusReason;
        this.resolvedFromHandlerMethod = handlerMethod;
        this.description = handlerMethod.description;
    }

    private MethodParameter[] initMethodParameters() {
        int count = this.bridgedMethod.getParameterCount();
        MethodParameter[] result = new MethodParameter[count];
        for (int i = 0; i < count; i++) {
            result[i] = new HandlerMethodParameter(i);
        }
        return result;
    }

    private void evaluateResponseStatus() {
        ResponseStatus annotation = getMethodAnnotation(ResponseStatus.class);
        if (annotation == null) {
            annotation = AnnotatedElementUtils.findMergedAnnotation(getBeanType(), ResponseStatus.class);
        }
        if (annotation != null) {
            String reason = annotation.reason();
            String resolvedReason = (StringUtils.hasText(
                    reason) && this.messageSource != null ? this.messageSource.getMessage(
                    reason, null, reason, LocaleContextHolder.getLocale()) : reason);

            this.responseStatus = annotation.code();
            this.responseStatusReason = resolvedReason;
        }
    }

    private static String initDescription(Class<?> beanType, Method method) {
        StringJoiner joiner = new StringJoiner(", ", "(", ")");
        for (Class<?> paramType : method.getParameterTypes()) {
            joiner.add(paramType.getSimpleName());
        }
        return beanType.getName() + "#" + method.getName() + joiner.toString();
    }


    /**
     * Return the bean for this handler method.
     */
    public Object getBean() {
        return this.bean;
    }

    /**
     * Return the method for this handler method.
     */
    public Method getMethod() {
        return this.method;
    }

    /**
     * This method returns the type of the handler for this handler method.
     * <p>Note that if the bean type is a CGLIB-generated class, the original
     * user-defined class is returned.
     */
    public Class<?> getBeanType() {
        return this.beanType;
    }

    /**
     * If the bean method is a bridge method, this method returns the bridged
     * (user-defined) method. Otherwise it returns the same method as {@link #getMethod()}.
     */
    protected Method getBridgedMethod() {
        return this.bridgedMethod;
    }

    /**
     * Return the method parameters for this handler method.
     */
    public MethodParameter[] getMethodParameters() {
        return this.parameters;
    }

    /**
     * Return the specified response status, if any.
     *
     * @see ResponseStatus#code()
     * @since 4.3.8
     */
    @Nullable
    protected HttpStatus getResponseStatus() {
        return this.responseStatus;
    }

    /**
     * Return the associated response status reason, if any.
     *
     * @see ResponseStatus#reason()
     * @since 4.3.8
     */
    @Nullable
    protected String getResponseStatusReason() {
        return this.responseStatusReason;
    }

    /**
     * Return the HandlerMethod return type.
     */
    public MethodParameter getReturnType() {
        return new HandlerMethodParameter(-1);
    }

    /**
     * Return the actual return value type.
     */
    public MethodParameter getReturnValueType(@Nullable Object returnValue) {
        return new ReturnValueMethodParameter(returnValue);
    }

    /**
     * Return {@code true} if the method return type is void, {@code false} otherwise.
     */
    public boolean isVoid() {
        return Void.TYPE.equals(getReturnType().getParameterType());
    }

    /**
     * Return a single annotation on the underlying method traversing its super methods
     * if no annotation can be found on the given method itself.
     * <p>Also supports <em>merged</em> composed annotations with attribute
     * overrides as of Spring Framework 4.2.2.
     *
     * @param annotationType the type of annotation to introspect the method for
     * @return the annotation, or {@code null} if none found
     * @see AnnotatedElementUtils#findMergedAnnotation
     */
    @Nullable
    public <A extends Annotation> A getMethodAnnotation(Class<A> annotationType) {
        return AnnotatedElementUtils.findMergedAnnotation(this.method, annotationType);
    }

    /**
     * Return whether the parameter is declared with the given annotation type.
     *
     * @param annotationType the annotation type to look for
     * @see AnnotatedElementUtils#hasAnnotation
     * @since 4.3
     */
    public <A extends Annotation> boolean hasMethodAnnotation(Class<A> annotationType) {
        return AnnotatedElementUtils.hasAnnotation(this.method, annotationType);
    }

    /**
     * Return the HandlerMethod from which this HandlerMethod instance was
     * resolved via {@link #createWithResolvedBean()}.
     */
    @Nullable
    public HandlerMethod getResolvedFromHandlerMethod() {
        return this.resolvedFromHandlerMethod;
    }

    /**
     * If the provided instance contains a bean name rather than an object instance,
     * the bean name is resolved before a {@link HandlerMethod} is created and returned.
     */
    public HandlerMethod createWithResolvedBean() {
        Object handler = this.bean;
        if (this.bean instanceof String) {
            Assert.state(this.beanFactory != null, "Cannot resolve bean name without BeanFactory");
            String beanName = (String) this.bean;
            handler = this.beanFactory.getBean(beanName);
        }
        // 其实就是拷贝属性
        return new HandlerMethod(this, handler);
    }

    /**
     * Return a short representation of this handler method for log message purposes.
     *
     * @since 4.3
     */
    public String getShortLogMessage() {
        return getBeanType().getName() + "#" + this.method.getName() + "[" + this.method.getParameterCount() + " args]";
    }


    private List<Annotation[][]> getInterfaceParameterAnnotations() {
        List<Annotation[][]> parameterAnnotations = this.interfaceParameterAnnotations;
        if (parameterAnnotations == null) {
            parameterAnnotations = new ArrayList<>();
            for (Class<?> ifc : ClassUtils.getAllInterfacesForClassAsSet(this.method.getDeclaringClass())) {
                for (Method candidate : ifc.getMethods()) {
                    if (isOverrideFor(candidate)) {
                        parameterAnnotations.add(candidate.getParameterAnnotations());
                    }
                }
            }
            this.interfaceParameterAnnotations = parameterAnnotations;
        }
        return parameterAnnotations;
    }

    private boolean isOverrideFor(Method candidate) {
        if (!candidate.getName()
                .equals(this.method.getName()) || candidate.getParameterCount() != this.method.getParameterCount()) {
            return false;
        }
        Class<?>[] paramTypes = this.method.getParameterTypes();
        if (Arrays.equals(candidate.getParameterTypes(), paramTypes)) {
            return true;
        }
        for (int i = 0; i < paramTypes.length; i++) {
            if (paramTypes[i] != ResolvableType.forMethodParameter(candidate, i, this.method.getDeclaringClass())
                    .resolve()) {
                return false;
            }
        }
        return true;
    }


    @Override
    public boolean equals(@Nullable Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof HandlerMethod)) {
            return false;
        }
        HandlerMethod otherMethod = (HandlerMethod) other;
        return (this.bean.equals(otherMethod.bean) && this.method.equals(otherMethod.method));
    }

    @Override
    public int hashCode() {
        return (this.bean.hashCode() * 31 + this.method.hashCode());
    }

    @Override
    public String toString() {
        return this.description;
    }


    // Support methods for use in "InvocableHandlerMethod" sub-class variants..

    @Nullable
    protected static Object findProvidedArgument(MethodParameter parameter, @Nullable Object... providedArgs) {
        if (!ObjectUtils.isEmpty(providedArgs)) {
            for (Object providedArg : providedArgs) {
                if (parameter.getParameterType()
                        .isInstance(providedArg)) {
                    return providedArg;
                }
            }
        }
        return null;
    }

    protected static String formatArgumentError(MethodParameter param, String message) {
        return "Could not resolve parameter [" + param.getParameterIndex() + "] in " + param.getExecutable()
                .toGenericString() + (StringUtils.hasText(message) ? ": " + message : "");
    }

    /**
     * Assert that the target bean class is an instance of the class where the given
     * method is declared. In some cases the actual controller instance at request-
     * processing time may be a JDK dynamic proxy (lazy initialization, prototype
     * beans, and others). {@code @Controller}'s that require proxying should prefer
     * class-based proxy mechanisms.
     */
    protected void assertTargetBean(Method method, Object targetBean, Object[] args) {
        Class<?> methodDeclaringClass = method.getDeclaringClass();
        Class<?> targetBeanClass = targetBean.getClass();
        if (!methodDeclaringClass.isAssignableFrom(targetBeanClass)) {
            String text = "The mapped handler method class '" + methodDeclaringClass.getName() + "' is not an instance of the actual controller bean class '" + targetBeanClass.getName() + "'. If the controller requires proxying " + "(e.g. due to @Transactional), please use class-based proxying.";
            throw new IllegalStateException(formatInvokeError(text, args));
        }
    }

    protected String formatInvokeError(String text, Object[] args) {
        String formattedArgs = IntStream.range(0, args.length)
                .mapToObj(i -> (args[i] != null ? "[" + i + "] [type=" + args[i].getClass()
                        .getName() + "] [value=" + args[i] + "]" : "[" + i + "] [null]"))
                .collect(Collectors.joining(",\n", " ", " "));
        return text + "\n" + "Controller [" + getBeanType().getName() + "]\n" + "Method [" + getBridgedMethod().toGenericString() + "] " + "with argument values:\n" + formattedArgs;
    }


    /**
     * A MethodParameter with HandlerMethod-specific behavior.
     */
    protected class HandlerMethodParameter extends SynthesizingMethodParameter {

        @Nullable
        private volatile Annotation[] combinedAnnotations;

        public HandlerMethodParameter(int index) {
            super(HandlerMethod.this.bridgedMethod, index);
        }

        protected HandlerMethodParameter(HandlerMethodParameter original) {
            super(original);
        }

        @Override
        @NonNull
        public Method getMethod() {
            return HandlerMethod.this.bridgedMethod;
        }

        @Override
        public Class<?> getContainingClass() {
            return HandlerMethod.this.getBeanType();
        }

        @Override
        public <T extends Annotation> T getMethodAnnotation(Class<T> annotationType) {
            return HandlerMethod.this.getMethodAnnotation(annotationType);
        }

        @Override
        public <T extends Annotation> boolean hasMethodAnnotation(Class<T> annotationType) {
            return HandlerMethod.this.hasMethodAnnotation(annotationType);
        }

        @Override
        public Annotation[] getParameterAnnotations() {
            Annotation[] anns = this.combinedAnnotations;
            if (anns == null) {
                anns = super.getParameterAnnotations();
                int index = getParameterIndex();
                if (index >= 0) {
                    for (Annotation[][] ifcAnns : getInterfaceParameterAnnotations()) {
                        if (index < ifcAnns.length) {
                            Annotation[] paramAnns = ifcAnns[index];
                            if (paramAnns.length > 0) {
                                List<Annotation> merged = new ArrayList<>(anns.length + paramAnns.length);
                                merged.addAll(Arrays.asList(anns));
                                for (Annotation paramAnn : paramAnns) {
                                    boolean existingType = false;
                                    for (Annotation ann : anns) {
                                        if (ann.annotationType() == paramAnn.annotationType()) {
                                            existingType = true;
                                            break;
                                        }
                                    }
                                    if (!existingType) {
                                        merged.add(adaptAnnotation(paramAnn));
                                    }
                                }
                                anns = merged.toArray(new Annotation[0]);
                            }
                        }
                    }
                }
                this.combinedAnnotations = anns;
            }
            return anns;
        }

        @Override
        public HandlerMethodParameter clone() {
            return new HandlerMethodParameter(this);
        }
    }


    /**
     * A MethodParameter for a HandlerMethod return type based on an actual return value.
     */
    private class ReturnValueMethodParameter extends HandlerMethodParameter {

        @Nullable
        private final Object returnValue;

        public ReturnValueMethodParameter(@Nullable Object returnValue) {
            super(-1);
            this.returnValue = returnValue;
        }

        protected ReturnValueMethodParameter(ReturnValueMethodParameter original) {
            super(original);
            this.returnValue = original.returnValue;
        }

        @Override
        public Class<?> getParameterType() {
            return (this.returnValue != null ? this.returnValue.getClass() : super.getParameterType());
        }

        @Override
        public ReturnValueMethodParameter clone() {
            return new ReturnValueMethodParameter(this);
        }
    }

}
